Differential baroswitch

ABSTRACT

1. A differential baroswitch comprising: A FIRST CHAMBER, A SECOND CHAMBER, AND A THIRD CHAMBER BETWEEN THE FIRST AND SECOND CHAMBERS; A PRESSURE RESPONSIVE MOVABLE ELEMENT BETWEEN THE FIRST AND SECOND CHAMBERS; A PRESSURE RESPONSIVE MOVABLE ELEMENT BETWEEN THE SECOND AND THIRD CHAMBERS; VENT AND VALVE MEANS FOR OPENING THE FIRST CHAMBER TO AMBIENT ATMOSPHERIC CONDITIONS OR CLOSING SUCH CHAMBER AS DESIRED; MEANS FOR SEALING THE SECOND CHAMBER; MEANS FOR VENTING THE THIRD CHAMBER TO AMBIENT ATMOSPHERIC CONDITIONS AT ALL TIMES; SENSING MEANS CONNECTED TO THE PRESSURE RESPONSIVE MOVABLE ELEMENTS TO INDICATE A POSITION OF THE ELEMENTS.

United States Patent 1191 Taylor [45] 13, [5 DIFFERENTIAL BAROSWITCH3,723,684 3/1973 Greenwood 200/83 N 75 I t r: Geor e R. Ta l0r RockawaNJ. 1 men 0 g y y Primary Examiner-Malcolm F. Hubler [73] Assignee: TheUnited States of America as A m E in G E, Mo t e repres n y e r tary ofthe Attorney, A gent, orFirm- Edward J. Kelley; Herbert Army,Washington, DC. t [22] Filed: June 3, 1964 A l N 372 427 EXEMPLARY CLAIM0.: pp l. A differential baroswitch comprlsmg:

a first chamber, a second chamber, and a third [52] US. Cl 200/83 N,73/386, 73/387, Chamber between the fi and Second Chambers; 73/406-200/83 A a pressure responsive movable element between the [51] Int. Cl.H0lh 35/34 fi and Second chambers; F ield of Search 200/81, 83; 73/384-386% a pressure responsive movable element between the 73/387, 389, 406,409, 178 second and third chambers;

vent and valve means for opening the first chamber References Cited toambient atmospheric conditions or closing UNITED STATES PATENTS suchchamber as desired;

19,079 2/1934 Kollsman 73/387 means for Sealing the SeCOPd Chamber?1,866,660 7/1932 Luckey 73 386 means for ventmg the th1rd chamber toamblent 2,883,485 4/1959 Willard 73/386 atmospheric conditions at alltimes;

2.883995 /1 5 Bia u 73/406 X sensing means connected to the pressureresponsive 9 1 Hobmugh 73/384 movable elements to indicate a position ofthe 3,021,865 2/1962 Beckett 73/388 elements. 3,209,721 l0/l965 Pull r73/406 3,246,093 4/1966 Bocttingcr 200/83 N 7 Claims, 5 Drawing FiguresALTITUDE PRE-SETHNG iscnzw 71x15 L/ PIVOT L 3 a 6 CENTER CHAMBER 8ELECTRICAL conmcrs mmmmll CALIBRATION INSULATION BACK FILLED WITH SCREWf PRESSURE O 7 GAS 11 SEAL ELECTRICAL ELECTRICAL 5 CONTACT '5 LEAD LEADBELOWS INSULATION 28 at PRESSURE SEAL 15 F 2 q LAUNCH sma PRESSURE PORTCASE 21 ALTITUDE PRE- SETTING SCREW PAIENIEDMIWW 3.829.640

\ sum ear 2 SCREWS CENTER OF CURVATURE OF CONTACT 7 CENTER OF CURVATUREOF CONTACT 9 FIG. 5 FIG. 4

INVENTOR.

GEORGE R. TAYLOR BY W 0 DIFFERENTIAL BAROSWITCH The invention describedherein may be manufactured and used by or for the Government forgovernmental purposes, without the payment to me of any royalty thereon.

An ordinary baroswitch is one which is constructed and pre-set such thatits electrical contacts will close at a certain height above sea levelas the switch is carried up into the atmosphere. For example, thefactory may construct and adjust the switch unit to close at a certainlowered atmospheric pressure representing 5,000 feet above sea level. Ifsuch switch is taken aloft from a sea level location, the switch willclose at 5,000 feet above the launch location. However, if such switchis taken aloft from a 4,000 foot mountain, then it will close at only1,000 feet above the launch location.

The present invention is directed toward a baroswitch which will closeat a certain predetermined height above the launch location, for example5,000 feet above the launch location, regardless of whether the launchlocation is at sea level, 5,000 feet above sea level, or at any otherelevation. Further the present baroswitch is adjustable for pre-settingthe operating altitude. An additional adjustment is provided forbaroswitch calibration.

In the drawing:

F IG. 1 is a diagrammatic representation of the present inventionincludingadjustment means for altitude pre-setting and calibrating thebaroswitch;

FIG. 2 is a cross section of an engineering test model of the inventionwith changeable diaphragms for altitude setting purposes;

FIG. 3 and 4 are diagrammatic representations showing the effect ofadjusting the altitude setting screw of FIG. 1; and

FIG. 5 is a graph representing atmospheric pressures at variousaltitudes.

The present baroswitch has three chambers 1, 2, 3. Chamber 1 has adiaphragm wall 5 and a casing 6. Chamber 2 has a diaphragm 7 and easing8. Diaphragm 5 carries an electrical contact 9 with an electrical lead10 attached thereto. Diaphragm 7 carries an electrical contact 11 withan electrical lead 12.

Electrical contacts 9, 11 are preferably protected against corrosion byan inert gas contained within a lightweight bellows 13 which offerssubstantially zero resistance to movement of diaphragms 5, 7. Insulatingpressure seals 15 are used where electrical leads 10, 12 pass throughcases 6, 8.

Center chamber 3 has a bellows 19 connecting cases 6, 8 and has a port16 therein. Chamber 1 has a port 17 which may be closed by valve 18.Chamber 2 is preferably sealed with no port or vent to the outside.However, a closable port may be provided for changing the pressure inchamber 2 ifdesired. Such port is illustrated at 28 with valve 29through which pressure in chamber 2 could be lowered or raised. Frame 20houses the cases 6, 8. Screw 21 provides for adjustment of case 6 withdiaphragm wall 5 with respect to diaphragm wall 7. Turning the screw 21rotates case 6 with diaphragm wall 5 about the axis of screw 21 wherethis axis passes through the center of curvature of concave contact 9.Screw 21 changes the angle of movement of concave contact 9 relative toflat contact 11.

Screw 22 is the calibration screw. It is used at the factory to adjustthe spacing between the contacts to the proper value. Screw 22 passesthrough frame 20 and laterally advances or retreats case 8 withdiaphragm wall 7 and contact 11. Plate 23 upon which is mounted case 8and diaphragm wall 7 rides freely along tracks 24 provided on frame 20as screw 22 is rotated. The tracks are to maintain alignment of the case8 with diaphragm wall 7 with respect to case 6 and diaphragm wall 5.

FIG. 2 illustrates another form of the baroswitch. It will be noted thatthe basic elements in FIG. 2 are similar to those in FIG. 1, and aredesignated with corresponding primed numerals, except that theadjustment apparatus is different. In FIG. 2 diaphragm assemblies 5, 7may be exchanged for weaker or stronger diaphragms which require lesseror greater pressures to move them and bring contacts 9', 11' together.The pressure in chamber 2 regulated through valve 29' is used tocalibrate the baroswitch in this design.

OPERATION In FIG. 1 pressure chamber 2 is filled at the factory with gasto a predetermined pressure, preferably near zero absolute pressure tominimize temperature change effects on the gas and operation of thebaroswitch. Chamber 3 is always filled with air at the ambientatmospheric pressure. Valve 18 remains open until the baroswitch isready for launching. At the launch site valve 18 is closed so as to trapair in chamber 1 at the ambient air pressure. Thus at launch time,pressure in chambers 1 and 3 is equal and the pressure in chamber 2 isat the predetermined value set at the factory.

With valve 18 closed, the baroswitch unit is carried aloft. As itascends, pressure in chamber 3 bleeds off through port 16 to lower thepressure and pressure in chambers 1 and 2 remains substantiallyunchanged except that flexing of the diaphragms may enlarge chambers 1and 2 slightly and thus lower the pressure slightly. Diaphragms 5, 7 aremoved toward one another bringing contacts 9, 11 closer together untilthey close to thereby close a circuit between electrical leads 10, 12.

If the baroswitch unit is launched from sea level then pressure inchambers 1 and 3 is approximately 14.7 lbs/sq. in. at launch time.Pressure in chamber 2 is sealed at the preselected value, assumed at avery low pressure. As the baroswitch ascends the pressure in chamber 3bleeds off until, at the preselected altitude, the pressure differencebetween chambers 1, 3 and 2, 3 forces diaphragms 5, 7 inward and causescontacts 9, 11 to close.

Now assume that the unit is launched from a higher elevation, say 5,000feet. The present differential baroswitch will not close until anelevation of 5,000 feet above the launch site is reached, i.e., 10,000feet above sea level. The phenomena causing this action is as follows.

As the baroswitch is moved aloft up from sea level to the preselectedaltitude, say 5,000 feet above sea level, atmospheric pressure decreases(approximately) 2.7, from 14.7 to 12.0 lbs/sq. in., note FIG. 5. Thisdecrease in pressure would besufficient to cause diaphragms S and 7 toclose contacts 9, 11 if launching were from sea level. However, thechange in atmospheric pressure from 5,000 to 10,000 feet above sea leveldecreases only approximately by 2.2, from 12.0 to 9.8 lbs/sq. in. Thisdifferential is not as great as in the previous illustration and itwould appear that the pressure change would not cause the contacts toclose if the baroswitch were launched from the site elevation of 5,000feet. However, chamber 2 acts as an automatic compensating chamber. Dueto the fixed pressure in this chamber, diaphragm 7 and contact 11 moveto the left as the baroswitch unit is moved upwardly and atmosphericpressure in chamber 3 decreases. This movement of contact 1] issubstantially equal to the lessening rate of movement of diaphragm 5 asthe baroswitch is moved to successively higher launch site elvations. Inother words, taking the example of altitudes and pressures given above,as the baroswitch moves aloft to 5,000 feet from sea level with valve 18closed, a pressure differential of 2.7 lbs/sq. in. forces diaphragm 5and contact 9 to the right toward contact 11. If the baroswitch werelaunched from an elevation of 5,000 feet from sea level to a height of5,000 feet above the launch elevation this altitude change would resultin a pressure differential of only 2.2 lbs/sq. in. and therefore,diaphragm 5 and contact 9 would not move as far toward contact 11.Nevertheless, the com pensating chamber 2 would have automatically moveddiaphragm 7 and contact 11 to the left representing the initial riseof5,000 feet from sea level to the launch site and would continue tomove contact 11 to the left as the baroswitch ascends from the launchsite elevation at 5,000 feet up to 10,000 feet. Thus, whether thebaroswitch unit is launched from sea level or from 5,000 feet, or fromany other level, the contacts will close at the altitude for which theunit is preset.

FIG. 5 illustrates the exponential drop in atmospheric pressure atincreasing altitudes. Additional graphs, charts, tables, and formulaecould be presented to prove that the compensating chamber 2automatically compensates for the exponential change in atmosphericpressure and the differential rate of movement of diaphragm 5 andcontact 9 as the baroswitch is moved upwardly. However, this data isbased on known physical constants and is deened unnecessary to anunderstanding of how and why the invention operates. It can be proventhat a baroswitch as illustrated, once designed and engineered to closecontacts 9, 11 at X feet above the launch site where valve 18 is closed,will always close contacts 9, II at X feet above the launch site,regardless of whether the launch site is at sea level. at 10,000 or20,000 or 30,000 feet, or even if the launch site is in a valley belowsea level.

It is possible to change the height at which the contacts will close byany one of several methods. For example, in FIG. 2, parts such asdiaphragm 5' or 7 may be interchangeable with other stronger or weakerdiaphragms, by removing cover plates 6, 8. A greater or lesser pressurewill then move the contacts together. Thus, with one set of diaphragmsthe contacts will close at 5,000 feet, with other sets the closing willoccur at 10,000 feet, or at 25,000, or 100,000 feet or any otheraltitude.

Another method of changing the contact-closing height would be to changethe pressure in chamber 2. If this pressure were increased, thecontact-closing height would be lowered. However, the gas in chamber 2is subject to pressure changes, such as an increase on a hot summer daywhen the launch site temperature may be 100 F, or a decrease on a coldday when the temperature is zero F. This could cause error depending onthe season or launch site location, and could also cause error as thebaroswitch moves to higher and therefore colder altitudes. Therefore, itis deemed preferable to use a very low pressure (near perfect vacuum) inchamber 2 and vary the contact-closing height by other means such as byinterchanging parts described above or by the presetting means describedhereinafter.

In FIG. 1 altitude presetting screw 21 is used to adjust the angulartravel of contact 9 relative to contact 11. Case 6 is pivoted about theaxis of the altitude presetting screw 21. As will be noted from FIGS. 3and 4, the axis of screw 21 passes through the center of curvature ofcontact 9 and the surfaces of contacts 9 and 11 are spherical and flatrespectively. As screw 21 is turned, case 6 with diaphragm wall 5 isrotated about the screw axis 21 to thereby change the angle of the cases6, 8 and diaphragms 5, 7 relative to one another. If screw 21 isadjusted to set diaphragm wall 5 of case 6 parallel to diaphragm wall 7of case 8 then contacts 9, 11 will move straight toward one another asin FIG. 3. However, if screw 21 is adjusted to throw the diaphragm walls5, 7 out of parallelism, then contact 9 will move obliquely towardcontact 11. Thus, changing the setting of altitude presetting screw 21changes the angle of approach of the contacts as illustrated in FIGS. 3and 4. It will be noted that in FIG. 3, diaphragm 5 need move contact 9straight from line Y to line Y and diaphragm 7 need move contact 11,straight from line Y to line Y for a given contact-closing heightsetting. However, in FIG. 4, contact 9 will be to the left of line Ywhen contact 11 is at line Y. For the contact to close with diaphragmwall 5 rotated, as shown in FIG. 4, the baroswitch must be carriedfurther aloft. Therefore by rotating diaphragm wall 5 thecontact-closing height is changed. Additional graphs, charts, tables,and formulas could be presented to prove that rotating diaphragm wall 5about the axis of the altitude presetting screw will provide the meansfor presetting the contactclosing height of the baroswitch. Or, screw 21may be used to adjust the instrument just prior to launching tocompcnsate'for ambient atmospheric pressure changes. Or, screw 21 may beused to adjust the instrument to the desired height setting tocompensate for discrepancies among materials and workmanship in themanufacture of the baroswitch components. For example, ifone baroswitchhas diaphragms slightly stronger than others, offering greaterresistance to deflection, then screw 21 could be adjusted to compensatefor the offstandard diaphragms.

Other forms of apparatus could be used to achieve the functionsdescribed in the specific examples shown in the drawings and describedhereinabove, or to perform other similar functions. For example, thegeometric shape of the contacts the pivot point of the diaphragm wall,and the means for pivoting the diaphragm walls can be changed to changethe altitude setting range of the baroswitch and/or provide a remote setcapability.

I claim:

1. A differential baroswitch comprising:

a first chamber, a second chamber, and a third chamber between the firstand second chambers;

a pressure responsive movable element between the first and secondchambers;

a pressure responsive movable element between the second and thirdchambers;

vent and valve means for opening the first chamber to ambientatmospheric conditions or closing such chamber as desired;

means for sealing the second chamber;

means for venting the third chamber to ambient atmospheric conditions atall times;

sensing means connected to the pressure responsive movable elements toindicate a position of the elements.

2. A differential baroswitch as in claim 1 wherein the sensing meanscomprises electrical contacts adapted to close when the baroswitchreaches a predetermined altitude independent of site elevation withlowered pressure in the third chamber sufficient to move the pressureresponsive movable elements inwardly within the third chambersufficiently to close the electrical contacts.

3. A differential baroswitch as in claim 2 and:

means to protect the electrical contacts against corrosion.

4. A differential baroswitch as in claim 1 and:

means for adjusting the pressure responsive means relative to oneanother so as to vary the sensing characteristics of the sensing means.

5. A differential baroswitch as-in claim 4 wherein one of the presureresponsive means, to which the sensing means is connected, is adjustablymounted to move about a pivot and a second pressure responsive means ismounted on a plate movable along a guide rail and wherein the sensingmeans for the guide-rail pressure responsive means is an electricalcontact with a flat surface and the sensing means for the pivotedpressure responsive means is an electrical contact with a roundedcontact area which lies on the radius ofa circle with the pivot as thecenter thereof, such that adjustment of the adjusting means varies thesensing characteristics of the sensing means.

6. A differential baroswitch as in claim 1 wherein the pressureresponsive means are interchangeable with pressure responsive means ofdifferent characteristics to thereby vary the sensing characteristics ofthe sensing means.

7. A differential baroswitch as in claim 1 and means to vary thepressure in the second chamber.

1. A differential baroswitch comprising: a first chamber, a secondchamber, and a third chamber between the first and second chambers; apressure responsive movable element between the first and secondchambers; a pressure responsive movable element between the second andthird chambers; vent and valve means for opening the first chamber toambient atmospheric conditions or closing such chamber as desired; meansfor sealing the second chamber; means for venting the third chamber toambient atmospheric conditions at all times; sensing means connected tothe pressure responsive movable elements to indicate a position of theelements.
 2. A differential baroswitch as in claim 1 wherein the sensingmeans comprises electrical contacts adapted to close when the baroswitchreaches a predetermined altitude independent of site elevation withlowered pressure in the third chamber sufficient to move the pressureresponsive movable elements inwardly within the third chambersufficiently to close the electrical contacts.
 3. A differentialbaroswitch as in claim 2 and: means to protect the electrical contactsagainst corrosion.
 4. A differential baroswitch as in claim 1 and: meansfor adjusting the pressure responsive means relative to one another soas to vary the sensing characteristics of the sensing means.
 5. Adifferential baroswitch as in claim 4 wherein one of the pressureresponsive means, to which the sensing means is connected, is adjustablymounted to move about a pivot and a second pressure responsive means ismounted on a plate movable along a guide rail and wherein the sensingmeans for the guide-rail pressure responsive means is an electricalcontact with a flat surface and the sensing means for the pivotedpressure responsive means is an electrical contact with a roundedcontact area which lies on the radius of a circle with the pivot as thecenter thereof, such that adjustment of the adjusting means varies thesensing characteristics of the sensing means.
 6. A differentialbaroswitch as in claim 1 wherein the pressure responsive means areinterchangeable with pressure responsive means of differentcharacteristics to thereby vary the sensing characteristics of thesensing means.
 7. A differential baroswitch as in claim 1 and means tovary the pressure in the second chamber.